Semiconductor laser device

Abstract

A semiconductor laser device for radiating a laser beam from a double heterostructure section in which injected carriers having an energy source of the laser beam are confined consists of a compound semiconductor substrate with a prescribed lattice constant for loading the double heterostructure section, a lattice mismatched active layer with a first lattice constant which is 0.5% to 2.0% larger than the lattice constant of the substrate in the double heterostructure section for radiating the laser beam, a lattice mismatched cladding layer with a second lattice constant which is 0.2% to 2.0% smaller than the lattice constant of the substrate for confining the injected carriers in the active layer, and a cladding layer for confining the injected carriers in the active layer by co-operating with the lattice mismatched cladding layer.

What is claimed is: 
     
       1. A semiconductor laser device for radiating a laser beam from a double heterostructure section in which injected carriers having an energy source of the laser beam are confirmed, comprising: a compound semiconductor substrate with a prescribed lattice constant for loading the double heterostructure section;   a lattice mismatched active layer with a first lattice constant which is 0.5% to 2.0% larger than the prescribed lattice constant of the substrate in the double heterostructure section for radiating the laser beam, an energy band-gap of the lattice mismatched active layer being smaller than that of a crystal with the prescribed lattice constant from which the laser beam is radiated;   a lattice mismatched cladding layer with a second lattice constant which is 0.2% to 2.0% smaller than the lattice prescribed constant of the substrate for confining the injected carriers in the active layer, (1) the lattice mismatched cladding layer being arranged on one side of the active layer in the double heterostructure section, and   (2) an energy band-gap of the lattice mismatched cladding layer being larger than that of a crystal with the prescribed lattice constant which confines the injected carriers in the active layer; and     a cladding layer arranged on another side of the active layer in the double heterostructure section for confining the injected carriers in the active layer by co-operating with the lattice mismatched cladding layer.   
     
     
       2. A device according to the claim 1 in which the substrate is formed by a GaAs crystal, the lattice mismatched active layer is formed by an In 1-x  Ga x  P crystal where 0.26≦X≦0.44, and the lattice mismatched cladding layer is formed by an In 1-y  (Ga 0 .3 Al 0 .7) y  P crystal where 0.52≦Y≦0.70. 
     
     
       3. A device according to the claim 1 in which the substrate is formed by a GaAs crystal, the lattice mismatched active layer is formed by an In 1-x  Ga x  P crystal where 0.26≦X≦0.44, the lattice mismatched cladding layer is formed by an In 1-y  (Ga 0 .3 Al 0 .7) y  P crystal where 0.52≦Y≦0.70, and the cladding layer is formed by an In 0 .5 (Ga 0 .3 Al 0 .7) 0 .5 P crystal of which a lattice constant agrees with that of the substrate. 
     
     
       4. A device according to the claim 1 in which the conductive type of the lattice mismatched cladding layer is p type and the conductive type of the cladding layer is n type. 
     
     
       5. A device according to the claim 1 in which the substrate is formed by an n type GaAs crystal, the cladding layer is formed on the substrate by an n type In 0 .5 (Ga 0 .3 Al 0 .7) 0 .5 P crystal of which a lattice constant agrees with that of the substrate, the lattice mismatched active layer is formed on the cladding layer by an In 1-x  Ga x  P crystal where 0.26≦X≦0.44, and the lattice mismatched cladding layer is formed on the active layer by an p type In 1-y  (Ga 0 .3 Al 0 .7) y  P crystal where 0.52≦Y≦0.70. 
     
     
       6. A device according to the claim 1 further including: a ridge shaped cladding layer mounted on the double heterostructure section for transmitting the injected carriers to the double heterostructure section; and   a current blocking layer mounted on the double heterostructure section and surrounding the ridge shaped cladding layer for blocking the injected currents.   
     
     
       7. A device according to the claim 1 in which the thickness D (Å) of the lattice mismatched active layer is within a range from 100 Å to 400 Å and the lattice mismatch Δa/a (%) of the active layer satisfies   <Δ a/a≦200/D and 0.5≦Δa/a≦2.0,     and the thickness T (Å) of the lattice mismatched cladding layer is within a range from 100 Å to 1000 Å and the lattice mismatch Δb/b (%) of the lattice mismatched cladding layer satisfies     -200T≦Δb/b<0 and -0.2≦Δb/b≦-2.0.     
     
     
       8. A device according to the claim 7 in which the thickness D (Å) of the lattice mismatched active layer, the thickness T (Å) of the lattice mismatched cladding layer, the lattice mismatch Δa/a (%) of the lattice mismatched active layer, and the lattice mismatch Δb/B (%) of the lattice mismatched cladding layer satisfy a following equation   D×Δa/a+T×Δb/b=0.     
     
     
       9. A device according to the claim 1 in which the lattice mismatched active layer is fabricated by a quantum well structure formed by a quantum well and a barrier layer. 
     
     
       10. A device according to the claim 1 in which no natural superlattice structure is formed in the lattice mismatched cladding layer. 
     
     
       11. A device according to the claim 1 in which the compound semiconductor substrate is formed by a crystal with a prescribed lattice constant and has a specific plane direction which leans by a prescribed angle toward a predetermined direction equivalent to a <011> direction from a (100) plane. 
     
     
       12. In a semiconductor laser device for radiating a laser beam from a double heterostructure section in which injected carriers having an energy source of the laser beam are confined, comprising: a compound semiconductor substrate with a prescribed lattice constant for loading the double heterostructure section;   a latticed mismatched active layer with a first lattice constant which is 0.3% to 2.5% larger than the prescribed lattice constant of the substrate in the double heterostructure section for radiating the laser beam, an energy band-gap of the lattice mismatched active layer being smaller than that of a crystal with the prescribed lattice constant from which the laser beam is radiated;   a first cladding layer with no natural superlattice structure for confining the injected carriers in the active layer, (1) the first cladding layer being grown on one side of the lattice mismatched active layer in the double heterostructure section,   (2) the first cladding layer making an epitaxial junction with the active layer, and   (3) an energy band-gap of the first cladding layer being larger than that of a crystal with a natural superlattice regularly directed in a <111> direction which confines the injected carriers in the active layer; and     a second cladding layer grown on another side of the active layer in the double heterostructure section for confining the injected carriers in the active layer by cooperating with the first cladding layer.   
     
     
       13. A device according to the claim 12 in which the lattice mismatched active layer is formed by an In 1-x  Ga x  P crystal where 0.20≦X≦0.47. 
     
     
       14. A device according to the claim 12 in which the conductive type of the first cladding layer is p type and the conductive type of the second cladding layer is n type. 
     
     
       15. A device according to the claim 12 in which a ratio occupied by no natural superlattice structure portion in the first cladding layer is adjusted by shifting a growing temperature of the first cladding layer, a molecular ratio of a V-family material to a III-family material, the concentration of the injected carriers in the first cladding layer, and a growing rate of the first cladding layer. 
     
     
       16. A device according to the claim 12 in which the compound semiconductor substrate has a specific plane direction which leans by a prescribed angel toward a predetermined direction equivalent to a <011> direction from a (100) plane. 
     
     
       17. In a semiconductor laser device for radiating a laser beam by confining injected carriers having an energy source of the laser beam, comprising: a compound semiconductor substrate which is formed by a crystal with a prescribed lattice constant and has a specific plane direction which leans by a prescribed angel toward a predetermined direction equivalent to a <011> direction from a (100) plane;   a first cladding layer grown on the substrate at an epitaxial junction;   a lattice mismatched active layer with a first lattice constant which is 0.5% to 2.0% larger than the prescribed lattice constant of the substrate for radiating the laser beam, (1) the active layer being grown on the first cladding layer at an epitaxial junction, and     (2) an energy band-gap of the lattice mismatched active layer being smaller than that of a crystal with the prescribed lattice constant from which the laser beam is radiated; and   a second cladding layer grown on the active layer at an epitaxial junction for confining the injected carriers in the active layer by co-operating with the first cladding layer.   
     
     
       18. A device according to the claim 17 in which the lattice mismatched active layer is formed by an In 1-x  Ga x  P crystal where 0.26≦X≦0.44. 
     
     
       19. A device according to the claim 17 in which the specific plane direction of the compound semiconductor substrate leans in the range up to 15° toward the predetermined direction equivalent to the <011> direction from the (100) plane. 
     
     
       20. A device according to the claim 17 in which the thickness D (Å) of the lattice mismatched active layer is within a range from 100 Å to 400 Å and the lattice mismatch Δa/a (%) of the active layer satisfies   0<Δa/a≦200/D and 0.5≦Δa/a≦2.0.